There are two wildly contrasting cultural dates in the diary this coming month that seem unlikely to attract the same crowd. One is the British release on Wednesday of a bawdy American comedy about a foul-mouthed soft toy called Ted and the other is a BBC Prom celebrating the swingin' music of the golden era of Hollywood and Broadway songwriting. And yet the star of these mismatched entertainments is one and the same man: Seth MacFarlane.

MacFarlane, who will sing at the Albert Hall on 27 August before keeping a second date at Ronnie Scott's, is to fly into London from his Beverly Hills home shortly after Ted, his directorial debut, opens in cinemas. His first solo album, Music is Better than Words, will also be released in Britain to coincide with the visit, but it is for neither the cinema nor crooning that this smooth 38-year-old baritone is best known.

For more than a decade now, MacFarlane has been both hailed and railed against by television audiences as the "evil genius" behind the hit animated comedy shows Family Guy and American Dad! He is also believed to be the best-paid TV writer and director working in the world, with an estimated net worth of $100m, as a result of the colossal ratings his Emmy-award winning shows deliver for Fox, his home network.

Not content with material success, MacFarlane also cuts a glamorously subversive figure. Like the human hero of Ted, John Bennett, played by Mark Wahlberg, he has so far avoided growing up by continuing to obsess about his youthful interests. The writer still looks a long way from settling down to family life, too. (Last week some corners of the Hollywood media reported that film star Cameron Diaz was dating MacFarlane, or at least a MacFarlane lookalike, while a month before, there were excited reports of his impromptu singing performances alongside Rumer Willis, the 23-year old daughter of Demi Moore and Bruce Willis, at a party in his Los Angeles home following the American premiere of Ted.)

Yet somehow, while mucking about, MacFarlane has developed a sophisticated line in upsetting American values from inside one of the most conservative media organisations. An avowed Democrat, he campaigns outspokenly for gay rights and manages to offend the reasonable and right-thinking moral majority almost every time he pens an episode of his filthy-minded shows. Notable controversies in the 10-series history of Family Guy include a parody of Tom Cruise as a gay kidnapper, a determinedly insensitive treatment of the issue of domestic abuse, and a contested antisemitic version of the Disney song When You Wish Upon a Star from Pinocchio, which was never aired. MacFarlane was also recently in trouble after hosting a televised comedy "roasting" of the drug and drink-addled Charlie Sheen that played relentlessly on the cruel notion that the actor would soon be dead.

Some critics in America are not convinced that Ted has the power to shock that MacFarlane TV fans might have hoped for. The novice film director, who also co-wrote the script and stars as the voice of the eponymous talking cuddly bear, may have been upset by the New York Times's judgment that his film is largely "harmless" although "it swears like a 13-year-old boy with unlimited access to premium cable".

MacFarlane would certainly baulk at any suggestion that he is mellowing. His screenplay contains plenty of graphic sexual and scatological jokes, as well as knowing references to the conventions of traditional romcoms. There are entertainingly bizarre cameo appearances from actor Patrick Stewart and singer Norah Jones, too.

With a growing following for MacFarlane's singing, though, a different path is beckoning. While Family Guy has often featured trademark cutaway musical segments, some of them winning Emmy awards in their own right, a full-time musical career is now clearly an option.

When MacFarlane recently appeared on Piers Morgan's CNN chatshow, the host asked him, with lamentable use of dated mental health labels, if he felt he was "schizophrenic". MacFarlane agreed there was probably an irreconcilable conflict in his rival enthusiasms for show tunes and for vulgar cartoons, although he added that he believed the great American songbook was more tongue-in-cheek than people realise.

"The thing about this kind of music is it never really took itself that seriously," he told Morgan. "Even in the 50s, you know, when Sinatra and Dean and those guys were out there, even when they were singing the romantic ballads, there was sort of a sense of, 'Ah, who cares?' "

Born in Connecticut, MacFarlane claims he picked up his salty sense of humour from his family and more particularly from his mother, who would happily regale his friends with the story of how she once masturbated a dog. "There was nothing on Family Guy or any of the other shows that could offend her," her son has said.

While studying animation at Rhode Island school of design, MacFarlane developed an animated film called The Life of Larry as a degree project. It became a word-of-mouth hit and earned him a contract with Hanna-Barbera.

"I had no credits to my name, really. And they were not going to give me $1m to make a pilot. So they said, listen, if you can do this for $50,000, you can have a show," he has recalled.

Starting out in 1999, Family Guy was later briefly dropped by Fox in 2001. However, reruns of the show and DVD box sets became so popular that the TV network relented and it was promptly recommissioned. And so it was that America, and then Britain, came to know, if not to love, the Griffin family from New England, complete with Stewie, the English baby that wants to kill its mother, and Brian the urbane, cultured dog (both voiced by MacFarlane). Like Matt Groenig, creator of The Simpsons, or Trey Parker and Matt Stone, the men behind South Park, MacFarlane attacks conventional propriety from every angle, but gets away with it by disguising the assault inside a slapstick cartoon genre. He has described the animated satirical subculture to which he belongs as serving a noble function not unlike that of the New Yorker: "This is the televised translation of that".

In 2009, MacFarlane's closet musical talent began to fight back in earnest. He joined a line-up at the BBC Proms to sing selected hits from the great Hollywood musicals of Metro-Goldwyn-Mayer, alongside Curtis Stigers and classical singer Thomas Allen and under the baton of John Wilson, the feted English musician who, along with his orchestra, has singlehandedly revived many of Hollywood's lost film scores.

Since that unexpected appearance, MacFarlane has toured Britain with Wilson's orchestra and become a regular performer at numerous jazz clubs in Los Angeles, headlining at the Salt Lake City Jazz Festival in 2010. In the same year he signed a deal with Universal Republic to record a fully orchestrated album of classic show tunes from the 1940s and 1950s. The songs, hand-picked by MacFarlane from the work of Rodgers and Hammerstein and Lerner and Loewe, was released last autumn in America and well reviewed. The singer's strength as a performer lies not so much in his rich, capable voice but in his relaxed and charming delivery. He trained, it is no surprise to learn, with voice coaches Lee and Sally Sweetland, who also worked with Barbra Streisand and Frank Sinatra.

As one American music critic has noted, many fans of Family Guy, American Dad! and MacFarlane's newest animated sitcom, The Cleveland Show, may wonder what has happened to their comic hero once they have seen him step out behind the microphone in his tuxedo to the accompaniment of Wilson's lush strings. But then there will always be the solace of enjoying "the private joke of being able to give their grandparents a Christmas gift recorded by this sometimes-scourge of the American right".

In an excerpt from this week's Guardian Film Show Xan Brooks, Catherine Shoard and Peter Bradshaw review Seth MacFarlane's Ted, a romantic comedy in which a potty-mouthed teddy bear - brought magically to life by a wish - causes havoc as his owner grows up